MODEL PFE-1

CCD/TELESCOPE ADAPTER

Technical Manual and User’s Guide

OPTEC, Inc.OPTICAL AND ELECTRONIC PRODUCTS 199 Smith St.

Lowell, MI 49331U.S.A.

info@optecinc.com (616) 897-9351http://www.optecinc.com (616) 897-8229 FAX

Figure 1-1. Model PFE-1 shown with Lynxx PC and Celestron 8" Telescope.

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TABLE OF CONTENTSRevision 6 - January 2000

Section Page

1.0 INTRODUCTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .

1

2.0 THEORY OF OPERATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..

3

2.1 Purpose of the PFE-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .

3

2.2 Basic Mechanical Design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..

4

3.0 INSTALLATION PROCEDURES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..

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3.1 Mounting the PFE-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .

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3.2 Mounting Kits for CCD Cameras. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..

7

3.3 Reticle alignment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..

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4.0 TROUBLE-SHOOTING GUIDE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..

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5.0 JOHNSON UBVRI FILTERS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .

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6.0 WING FILTERS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .

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7.0 STRÖMGREN FILTERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .

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8.0 PFE-1A AUTOMATIC OPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .

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8.1 Physical Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..

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8.2 Determining Filter Position . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .

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8.3 Connecting & Operating the Stepper Motor. . . . . . . . . . . . . . . . . . . . . . .. .

19

8.4 Using the SAA1027 Stepper Driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..

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APPENDICES

A. PFE-1A Mounting Kit Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..

A-1

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LIST OF FIGURESFigure Page

1-1 PFE-1 shown with Lynxx PC and Meade 8" Telescope. . . . . . . . . . Cover

1-2 PFE-1 CCD Photometer System and Accessories. . . . . . . . . . . . . . 2

2-1 Cross-Sectional View of the PFE-1 mounted with CCD camera. . . 4

8-1 Typical Stepper Control Curcuit Using the SAA1027. . . . . . . . . . . . 20

LIST OF TABLESTable Page

5-1 Physical Characteristics of Optec UBVRI Filters. . . . . . . . . . . . . . 11

5-2 Standard UBVRI Response Functions According to Johnson. . . . . 12

5-3 UBVRI Response Functions of Optec Filters. . . . . . . . . . . . . . . . . 13

5-4 Filter Transmission and Detector Responsivity in A/W. . . . . . . . . 14

6-1 Specifications for Wing Filters. . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

7-1 Optical Specifications of the Strömgren Filters. . . . . . . . . . . . . . . . 16

7-2 Physical Specifications of the Strömgren Filters. . . . . . . . . . . . . . . 16

8-1 Specifications for Model PF35-48C Stepper Motor. . . . . . . . . . . . 18

8-2 Function and Color Code of Motor Wires. . . . . . . . . . . . . . . . . . ..

19

8-3 Pin Number and Function for Motor Control Cable Connector. . . . 20

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SECTION 1.0

INTRODUCTION

The recent advent of affordable astronomical CCD cameras has opened whole newopportunities in the area of stellar and extended object photometry. The small formatCCD cameras now being manufactured by companies such as Meade and SantaBarbara Instrument Group are examples of the new low-cost cooled-chip astro-nomical cameras. Regrettably, with these cameras alone it is difficult to find andcenter objects, focus the camera, and, most importantly for photometry, insert filtersinto the light path. Optec has developed the Model PFE-1 Photometric Front-End toprovide the much needed coupling between telescope and CCD camera head. Withthe PFE-1, easy and accurate photometric quality imaging is finally possible.

The Model PFE-1 was originally designed specifically for the Lynxx PC CCD camerasystems, but has now been adapted for many small format cameras as well. Consultthe current price list for additional adapter kits for new cameras supported by thePFE-1.

The PFE-1 is a complete system with many filter options, a 0.5x telecompressor and3x tele-extender options, and a fully automated filter slider option.

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Figure 1-2. PFE-1A CCD Photometer System.

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SECTION 2.0

THEORY OF OPERATION

2.1 PURPOSE OF THE MODEL PFE-1

Two of the most serious limitations to doing photometry with the small format CCD camerasare small field sizes and lack of a convenient way to insert photometric filters into the lightpath. The PFE-1 provides an off-the-shelf solution to both these problems.

The TC-211 CCD chip used in the SBIG ST-4 and Lynxx PC series cameras has anarray of 165 pixels by 192 pixels. The chip is only about 1/10th inch square and thereforeoffers a very small field-of-view. Finding and centering an object can be difficult withoutsome sort of pre-viewer. Off-axis guiders do not provide full-field views and are of limiteduse. However, the eyepiece of the PFE-1 provides a full field view (approximately 0.4° withan 8" f/10) and an illuminated reticle which exactly defines the CCD detector field of view.Locating and centering an object with the PFE-1 is as simple as looking through theeyepiece, positioning the telescope, and opening the flip-mirror.

Because of the limited field size, to properly perform differential photometry a separateimage is often required for both the check and comparison stars. To effectively double thefield-of-view, Optec offers the 0.5X telecompressor (stock no. 17610) mounted in aremovable 1¼" telescope coupler. This option can be used with light cones of f/10 or higherwithout vignetting when using cameras having CCD's no larger than about 3.3mm by 2.4mmsize.

For planetary imaging, a 3x tele-extender (stock no. 17611) triples the effective focal lengthof the telescope system. A well corrected negative achromat is used in the tele-extender forunparalled planetary images.

The other important issue for any photometric use of a CCD is filters. The PFE-1 has a filterport directly behind the flip-mirror which allows the use of ½" diameter photometric filters.The standard PFE-1 requires the filters to be mounted in 2-position filter sliders (stock no.17050). The automated version PFE-1A includes a stepper motor and can use the 6-positionfilter sliders which are controlled by the SSPCARD and computer. See Section 9.0 for fulldetails of the automated option.

Johnson, Strömgren, Wing, and Hß filters are available in ½" diameter sizes directly fromOptec. Refer to Sections 5.0 through 8.0 for additional information on our filterspecifications for photometry.

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2.2 BASIC MECHANICAL DESIGN

Figures 2-1 shows cross-sectional views of the PFE-1 when mounted to a CCD camera head.Light enters the PFE-1 through the 1¼ inch telescope adapter and is directed either to thefocusing eyepiece or the CCD sensor by means of a flip-mirror. The focusing eyepiececonsists of a 1-inch (25.4mm) focal length Ramsden and a reticle with a precisely etchedsquare that defines the CCD field of view. A green LED illuminates the reticle from theside. After a star is positioned in the reticle, the flip mirror is rotated to expose the CCD.An exposure may now by made using the camera's control software.

Figure 2-1. Cross-sectional view of the PFE-1A mounted to a CCD camera.

The removable 1¼-inch telescope coupler attaches to any standard 1¼ inch focuser. Anoptional 2-inch focusing mount adapter is available from Optec for attachment to the largerformat telescope focusers. The standard 1¼-inch coupler can be replaced with a removable1¼-inch coupler containing a 0.5X telecompressor lens (stock no. 17610) or a 3X tele-extender lens (stock no. 17611).

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On the bottom of the PFE-1 flip mirror/eyepiece assembly is an input jack for the 12 VDCrequired to provide power to the reticle LED. The external DC power supply adapter shouldbe plugged in before operation. To adjust the reticle brightness on the PFE-1, use a smallscrewdriver to turn the pot next to the power input jack. The PFE-1A has an adjustmentknob to facilitate changing the reticle brightness.

For the PFE-1, a two-position filter slider is mounted between the flip mirror and the CCD.Any pair of filters selected by the user before delivery can be mounted in the slider. Sincethe slider is easily pulled out of the unit, sliders with other combinations of filters can beinserted.

The automated PFE-1A uses a 6-position filter slider made of a special self-lubricatingmaterial. A rack mounted on the slider meshes with a bevel gear connected to the steppermotor which is mounted beneath the main flip-mirror block. The 6-position filter sliders canbe pulled out and replaced, but this procedure requires removing one of the filter slidercovers. By replacing these larger capacity sliders, other photometric filter systems can beaccommodated.

For most variable star work, a single slider with B and V filters is recommended to beginwith. All Optec filters are ½" (12.7mm) in diameter and 7mm thick. See Section 6.0 for adescription of the standard UBVRI filter system, Section 7.0 for a description of the MA,MB and MI Wing filter set, and Section 8.0 for a description of the Strömgren uvby four-color system.

For observations which do not require a photometric filter, the Clear filter should used toinsure that the proper optical distance is maintained. Without the Clear filter, the eyepiecewould no longer be parfocal with the CCD and stellar images will be out of focus on theCCD sensor.

For tri-color imaging (RGB), the Johnson B, V, and R filters can be used. Since each filterblocks the infrared, no separate IR blocking filter is needed.

To adapt the Model PFE-1 to the various CCD camera heads available, Optec has designed anumber of special mounting kits. These kits provide all the necessary hardware includingmounting screws and allen keys for adapting the PFE-1 to a particular camera head. Referto Appendix A for full instructions regarding the mounting kits. The reticle alignmentprocedure is detailed in Section 3.3 below.

Owners of the Lynxx PC, MC, or Lynxx 2 CCD camera systems should order mounting kitstock number 17612. The standard combination 2"/1¼" telescope coupler provided bySpectraSource Instruments is replaced with a stainless steel camera mounting adapter. Thisspecial camera mount is secured to the camera head with three small screws. Specifymounting kit number 17613 for use with a standard C-mount camera. This kit includes adovetail plate and the (approx.) 1” diameter male C-thread for easy attachment of a typicalC-mount video camera.

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Mounting kit stock number 17614 will adapt the Santa Barbara Instrument Group's ModelST-4 CCD camera to the PFE-1. The 1¼" telescope mount of the ST-4 includes a smallcover window and O-ring seal. Mounting kit number 17614 includes a special spacer whichcontains a replacement cover window and O-ring seal. The stainless steel camera mountthen attaches to this spacer and the PFE-1 attaches to the camera mount. Again, allmounting screws and tools are included with the mounting kit. To gain additional field ofview, the eyepiece mount used on the PFE-1 is slightly shorter for the ST-4. Be sure tospecify mounting kit number 17614 when ordering a PFE-1 for use with the ST-4.

Mounting kit stock number 17615 will adapt the Santa Barbara Instrument Group's ModelST-5 CCD camera to the PFE-1. Like the Lynxx-2000, the ST-5 uses the TC-255 CCD andmust also have a rectangular reticle mounted in the focusing eyepiece of the PFE-1.Otherwise, mounting kit number 17615 is identical to number 17614 and installs in the samemanner.

Specify mounting kit number 17616 to adapt the PFE-1 to Meade's Pictor 416 camera. ThePictor 416 uses a Kodak KAF-0400 CCD with a rectangular imaging area. This CCDfeatures 768 x 512 pixels and is 6.90 x 4.60mm in size. When this kit is ordered, therectangular reticle installed in the PFE-1 matches this shape and size. The stainless steelmount simply screws into the camera head and replaces the existing 1¼" telescope adapter.

Owners of the Celestron/SBIG PixCel 255 camera should specify mounting kit number17618. The PixCel adapter is unique in that it allows the CCD camera to be removed fromthe PFE-1 much like a standard camera lens. Bot focus and rotational alignment aremaintained with camera removal and attachment. This feature allows the PixCel camera tobe easily used with both the PFE-1 and the MAXfield 0.33X telecompressor product.Changing between the PFE-1 flip-mirror and the MAXfield telecompressor is as easy aschanging a 35mm camera lens.

With the proper CCD camera mounting kit, the PFE-1 flip-mirror/eyepiece assembly is thenattached to the camera. A dovetail mount on the camera side and four setscrews on thePFE-1 side provide adjustment in the X and Y directions. Reticle alignments are easily doneon the Optec optical bench or at the telescope.

The CCD camera head completes the portion of the CCD photometer which is installed onthe telescope. Typically, a multiconductor cable will connect the CCD photometer head tothe host computer or control box. Refer to the user manual provided with your camera orcontrol software.

Optec will install the PFE-1 with any camera at no charge and will perform the reticlealignment on an optical bench for initial purchases. Subsequent reticle alignments can beperformed for a nominal charge. The entire camera outfit including camera head, control boxor interface card, and software should be sent to Optec for installation. Consult the currentprice list for additional cameras supported. Contact Optec for adapting the PFE-1 to anycameras not shown on the current price list.

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SECTION 3.0

INSTALLATION PROCEDURES

3.1 MOUNTING THE PFE-1

Installation of the PFE-1 to one of the cameras should be done in a clean area free of dustand other contaminants. The procedure is not difficult and all necessary tools are providedwith the mounting kits. However, as with any delicate optical device, care should be takenwhen handling the camera.

For first time buyers who prefer not to attempt mounting the PFE-1, Optec will perform theinstallation and reticle alignment free-of-charge. This will, of course, require sending thecamera head and control electronics to Optec. Re-alignments will also be performed for anominal fee. Call Optec for details.

3.2 MOUNTING KITS FOR CCD CAMERAS

Optec offers a variety of mounting kits for the various CCD cameras which are compatiblewith the PFE-1. Consult the current price list for a list of the latest cameras supported.Appendix A provides step-by-step instructions for attaching the mounting plate to thecamera.

3.3 RETICLE ALIGNMENT

After attaching the CCD camera to the mounting plate

Note that there are four setscrews around the square body of the PFE-1 directly in front ofthe CCD camera head. These setscrews allow adjustment in the X and Y directions. Roughalignment should bring the image as viewed through the eyepiece fairly close to the imageseen on the computer monitor. The camera head may need to rotated in the X-Y mountslightly to match up the orientation.

To perform the reticle alignment at the telescope, slide the telescope coupler into the focustube of the telescope. If using a Schmidt-Cassegrain type telescope remove the diagonalfrom the visual back. The X and Y adjustments should be fairly close from the roughalignment, but the camera will need to be rotated to line up with the square reticle. Be sure afilter is inserted in the filter port. A Johnson V filter is recommended since this filter mostclosely matches the photopic response of the eye.

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In the telescope, locate a fairly bright extended object such as the moon or a distant streetlamp and center it in the reticle. Put the control software in the Focus mode and slightlyloosen the setscrews to allow camera rotation. Rotate the camera and make the final X-Yadjustments so that the view within the reticle matches the view on the video monitor.The full-frame focus mode works best. Take your time. The reticle alignment can befrustrating if rushed, but if the approach is methodical the entire procedure can beaccomplished in about 10 minutes. Tighten the four setscrews securely against the stainlesssteel dovetail mount. As long as the camera is not removed, no realignment should benecessary.

The eyepiece height and orientation is set at Optec for each specific mounting kit. If dust onthe reticle is troublesome, remove it by blowing air (canned air for camera cleaning issuggested) through the 1¼" telescope coupler. Do not, in any case, remove the eyepiecefrom the assembly.

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SECTION 4.0

TROUBLE-SHOOTING GUIDE

The following common problems and solutions have been collected over the yearsfrom our customers and our attempts to solve their instrument problems. Beforecalling us, read through these and relevant sections of this manual to see if an easysolution exists for your errant photometer.

The CCD photometer seems to produce erratic results with the I and R filters butappears to work OK with the B and V filters.

Read section 3.1 again. In addition to observatory or nearby incandescent light causingproblems, high cirrus clouds not visible with the naked eye or an active aurora can causehavoc in the far red and infrared portions of the spectrum and be invisible in the visibleportion.

The night appears clear but the star count is diminishing with time faster thanexpected due to changing extinction conditions.

A common problem specially with Celestron and Meade telescopes is that a nearly invisiblefilm of condensed water will develop on the corrector plate or main mirror during the night ifthe dew point is high enough. Usually this fog film can only be seen when a strong light isprojected down the front of the telescope and the optics carefully inspected. A hair dryer is agood cure.

When using the PFE-1A and moving the filter slider, a clicking noise is heard but thefilter slide does not actually move.

If the filter slider covers have been removed for any reason, they may be binding against theslider. To check, simply loosen the two pan head screws on either of the covers and movethe filter slider from the keyboard. Carefully tighten the screws while ensuring that the slidercontinues to move. If this does not cure the problem, a return to Optec may be required.

The long term performance of the CCD seems to be seasonal. The limiting magnitudeduring the summer months cannot seem to match the limiting magnitudes during thewinter months.

This phenomena is due to the nature of the TEC cooler. The coolers on some CCD camerasare not regulated. The operating temperature is much lower during winter nights than duringsummer nights because ambient temperatures during the summer months may be 20° (ormore) higher than typical winter ambient temperatures. With lower operating temperatures,

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the S/N ratio will be lowered. Remember, for each 10°C drop in operating temperature again of about one stellar magnitude is achieved in limiting magnitude.

The focus seems to shift significantly throughout the evening.

Focus is a common problem among the Schmidt-Cassegrain type telescopes. With the foldedoptical path of the SCT, slight thermal changes have a significant effect on the overall focusof the system. You should routinely check the focus by using the focus mode of the dataacquisition software. Most of the standard CCD control software packages offer a focusmode. An even better solution is the Optec TCF temperature compensating focuser. Visitthe Optec website at www.optecinc.com for more details.

The telescope is properly balanced, but in certain directions the tracking seems lessthan adequate.

With CCD imaging, proper balance and polar alignment is essential. Any slight movement indeclination or right ascension can result in a blurred image. Remember that each pixel is onlyabout 10 microns, so even a slight nudge will show up in the final image. Try fastening thecables of the CCD camera head directly to the telescope fork arms with tape or zip-ties. Thekey is to remove as much stress from the photometer head as possible. Another safety tipfor SCT owners is to add a second thumbscrew to the visual back. Drill and tap the holesuch that the two thumbscrews are 90° apart. When installing the CCD photometer tightenboth thumbscrews to avoid a catastrophic fall.

When observing a number of faint variables, glare from the reticle makes it difficult tocenter the object.

PFE-1A users have the luxury of simply adjusting the reticle brightness with the large knobon the bottom of the unit. Standard PFE-1 users will need a small screwdriver to adjust thepot on the underside of the unit near the reticle power supply jack.

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SECTION 5.0

JOHNSON UBVRI FILTERS

The UBVRI filter system established by Johnson is generally followed today and definescolor bands in the spectrum interval from 300 to 1200 nm. Table 5-2 lists the filter-detectorresponses of this system as originally established by Johnson. Filter-detector response isdefined as the normalized product of filter transmission times detector response for eachwavelength interval. Table 5-3 lists the response functions of the UBVRI filters and Table 5-4 lists the filter-detector responses for the filters used with the Texas Instruments TC-211CCD device.

The OPTEC UBVRI filters are all made from combinations of Schott colored glass. Theglass types and thickness for each filter has been computer optimized for the best fit with theJohnson standards.

As can be seen from Tables 5-2 and 5-3, the B, V, R and I filters match closely the standardJohnson values and give correspondingly small correction coefficients. Blocking the redleak of the glass used in the U filter results in loss of UV transmission from 300 to 350 nm.The filter is still useful for comparison purposes even though it does not transform into thestandard Johnson system precisely. It is interesting to note that the U filter is the mostdifficult one to transform accurately for all observers including those with photomultipliersystems. UV transmission through the atmosphere varies considerably and any optical glassin the telescope (corrector lens) or photometer will absorb light shorter than 350 nm makingaccurate U magnitude determinations difficult at best.

For those persons interested in the exact filter transmission and detector responsivity, Table5-4 has been prepared using the latest filter and detector batch data. Filter characteristics aresubject to change since we continually review our filter formulas and attempt to achievesmaller transformation coefficients.

Flatness 6 fringes maximumSurface Quality scratch and dig 80-50

Diameter 12.7 mmThickness 7 mm

Table 5-1. Physical Characteristics of Optec UBVRI Filters.

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nm U B V R I300 0.00 ----- ----- ----- -----310 0.10 ----- ----- ----- -----320 0.61 ----- ----- ----- -----330 0.84 ----- ----- ----- -----340 0.93 ----- ----- ----- -----350 0.97 ----- ----- ----- -----360 1.00 0.00 ----- ----- -----370 0.97 ----- ----- ----- -----380 0.73 0.11 ----- ----- -----390 0.36 ----- ----- ----- -----400 0.05 0.92 ----- ----- -----410 0.01 ----- ----- ----- -----420 0.00 1.00 ----- ----- -----440 ----- 0.94 ----- ----- -----460 ----- 0.79 0.00 ----- -----480 ----- 0.58 0.02 ----- -----500 ----- 0.36 0.38 ----- -----520 ----- 0.15 0.91 0.00 -----540 ----- 0.04 0.98 0.06 -----560 ----- 0.00 0.72 0.28 -----580 ----- ----- 0.62 0.50 -----600 ----- ----- 0.40 0.69 -----620 ----- ----- 0.20 0.79 -----640 ----- ----- 0.08 0.88 -----660 ----- ----- 0.02 0.94 -----680 ----- ----- 0.01 0.98 0.00700 ----- ----- 0.01 1.00 0.01720 ----- ----- 0.01 0.94 0.17740 ----- ----- 0.00 0.85 0.36760 ----- ----- ----- 0.73 0.56780 ----- ----- ----- 0.57 0.76800 ----- ----- ----- 0.42 0.96820 ----- ----- ----- 0.31 0.98840 ----- ----- ----- 0.17 0.99860 ----- ----- ----- 0.11 1.00880 ----- ----- ----- 0.06 0.98900 ----- ----- ----- 0.04 0.93920 ----- ----- ----- 0.02 0.84940 ----- ----- ----- 0.01 0.71960 ----- ----- ----- 0.00 0.58980 ----- ----- ----- ----- 0.47

1000 ----- ----- ----- ----- 0.361020 ----- ----- ----- ----- 0.281040 ----- ----- ----- ----- 0.201060 ----- ----- ----- ----- 0.151080 ----- ----- ----- ----- 0.101100 ----- ----- ----- ----- 0.081120 ----- ----- ----- ----- 0.051140 ----- ----- ----- ----- 0.03

Table 5-2. Standard UBVRI Response Functions According to Johnson.

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nm U B V R I300 0.00 ----- ----- ----- -----310 0.00 ----- ----- ----- -----320 0.00 ----- ----- ----- -----330 0.13 ----- ----- ----- -----340 0.33 ----- ----- ----- -----350 0.50 0.00 ----- ----- -----360 0.77 0.02 ----- ----- -----370 1.00 0.10 ----- ----- -----380 0.92 0.22 ----- ----- -----390 0.53 0.42 ----- ----- -----400 0.00 0.60 ----- ----- -----410 0.00 0.72 ----- ----- -----420 0.00 0.87 ----- ----- -----440 ----- 1.00 ----- ----- -----460 ----- 0.76 0.00 ----- -----480 ----- 0.50 0.00 ----- -----500 ----- 0.33 0.52 ----- -----520 ----- 0.17 0.89 ----- -----540 ----- 0.08 1.00 0.00 -----560 ----- 0.05 0.96 0.06 -----580 ----- 0.05 0.75 0.27 -----600 ----- ----- 0.36 0.50 -----620 ----- ----- 0.13 0.63 -----640 ----- ----- 0.04 0.85 -----660 ----- ----- 0.00 1.00 -----680 ----- ----- 0.00 1.00 0.00700 ----- ----- 0.00 0.88 0.00720 ----- ----- ----- 0.84 0.00740 ----- ----- ----- 0.75 0.00760 ----- ----- ----- 0.57 0.11780 ----- ----- ----- 0.38 0.52800 ----- ----- ----- 0.24 0.80820 ----- ----- ----- 0.18 0.95840 ----- ----- ----- 0.14 1.00860 ----- ----- ----- 0.09 0.89880 ----- ----- ----- 0.05 0.70900 ----- ----- ----- 0.03 0.57920 ----- ----- ----- 0.01 0.41940 ----- ----- ----- 0.01 0.28960 ----- ----- ----- 0.00 0.20980 ----- ----- ----- ----- 0.15

1000 ----- ----- ----- ----- 0.101020 ----- ----- ----- ----- 0.061040 ----- ----- ----- ----- 0.041060 ----- ----- ----- ----- 0.021080 ----- ----- ----- ----- 0.011100 ----- ----- ----- ----- 0.001120 ----- ----- ----- ----- 0.001140 ----- ----- ----- ----- 0.00

Table 5-3. UBVRI Response Functions of the Optec Filters.

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nm U B V R I DET. A/W*300 0.00 ----- ----- ----- ----- -----310 0.00 ----- ----- ----- ----- -----320 0.00 ----- ----- ----- ----- -----330 0.16 ----- ----- ----- ----- 0.013340 0.28 ----- ----- ----- ----- 0.019350 0.37 0.00 ----- ----- ----- 0.022360 0.48 0.04 ----- ----- ----- 0.026370 0.49 0.14 ----- ----- ----- 0.033380 0.39 0.28 ----- ----- ----- 0.038390 0.17 0.41 ----- ----- ----- 0.050400 0.00 0.50 ----- ----- ----- 0.058410 ----- 0.55 ----- ----- ----- 0.063420 ----- 0.60 ----- ----- ----- 0.070440 ----- 0.57 ----- ----- ----- 0.085460 ----- 0.39 ----- ----- ----- 0.095480 ----- 0.21 0.00 ----- ----- 0.115500 ----- 0.11 0.49 ----- ----- 0.145520 ----- 0.05 0.74 ----- ----- 0.165540 ----- 0.02 0.72 0.00 ----- 0.190560 ----- 0.01 0.60 0.04 ----- 0.220580 ----- 0.01 0.40 0.16 ----- 0.255600 ----- ----- 0.21 0.33 ----- 0.235620 ----- ----- 0.08 0.44 ----- 0.220640 ----- ----- 0.02 0.50 ----- 0.260660 ----- ----- 0.00 0.53 ----- 0.290680 ----- ----- 0.00 0.51 ----- 0.300700 ----- ----- 0.00 0.46 ----- 0.295720 ----- ----- ----- 0.41 0.00 0.315740 ----- ----- ----- 0.34 0.00 0.340760 ----- ----- ----- 0.27 0.08 0.325780 ----- ----- ----- 0.21 0.45 0.275800 ----- ----- ----- 0.16 0.81 0.235820 ----- ----- ----- 0.11 0.90 0.250840 ----- ----- ----- 0.08 0.91 0.260860 ----- ----- ----- 0.06 0.90 0.235880 ----- ----- ----- 0.04 0.89 0.185900 ----- ----- ----- 0.03 0.87 0.155920 ----- ----- ----- 0.02 0.84 0.115940 ----- ----- ----- 0.01 0.81 0.082960 ----- ----- ----- 0.01 0.77 0.062980 ----- ----- ----- 0.01 0.72 0.048

1000 ----- ----- ----- 0.01 0.66 0.0351020 ----- ----- ----- ----- 0.57 0.0261040 ----- ----- ----- ----- 0.49 0.0171060 ----- ----- ----- ----- 0.38 0.0151080 ----- ----- ----- ----- 0.28 0.0101100 ----- ----- ----- ----- 0.20 -----1120 ----- ----- ----- ----- 0.14 -----1140 ----- ----- ----- ----- 0.08 -----

Table 5-4. Filter Transmission and Detector Responsivity in A/W.* Approximate values for a typical charge coupled device.

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SECTION 6.0

WING FILTERS

With the cooperation of Dr. Robert F. Wing of Ohio State University, Optec has designedthree filters for the SSP-3 photometer which are useful in measuring the absorption of TiO(titanium oxide), and the true color temperature of late type stars such as Miras. These

three filters labeled MA, MB and MI comprise a subset of the Wing 8-color system1. See

Table 6.1 for filter specifications.

It is widely known that the B-V color index of stars with spectral type K5 to M8 is nearlyconstant although the surface temperature of stars in this range vary considerably. The coolerthe surface temperature of these stars the greater the TiO absorption in the visual band,which prevents the color index from becoming redder. As a result, the common B and Vmagnitude contain little useful information about these stars.

Used together, the MA and MB filters measure the amount of TiO absorption in the star'souter atmosphere. The MA filter is centered on an absorption band at 712 nm and the MBfilter is centered just off the band and on the continuum at 754 nm. The ratio of readingstaken with these filters is proportional to the amount of TiO absorption.

The MI filter is centered on the continuum at 1025 nm. Readings taken with this filter and theMB filter can be used together to measure the slope of blackbody curve between these twopoints, and thus the temperature of the star may be calculated.

Because these stars radiate most of their energy in the infrared and the TC-211 CCD chip issensitive for part of this band, very good stellar images can be obtained with these filterswhen only marginal images are obtained in the Johnson B and V bands. This is partiallytrue because the amount of background light from the atmosphere due to scatter from themoon or ground lights is extremely low in the infrared wavelengths. Thus, good Wingphotometry can be performed even when B and V photometry is impossible because of brightbackground sky noise.

FILTER CENTER BANDPASS PEAKNAME WAVELENGTH 1/2T POINTS TRANSMISSION

MA 712 nm 10 nm 75 %MB 754 nm 10 nm 75 %MI 1025 nm 40 nm 55 %

Table 6-1. Specifications for Wing Filters.

1 Wing, R. F., 1971, Proceedings of the Conference on Late Type Stars,ed. G.W. Lockwood and H. M. Dyck(KPNO Contribution No. 554), p. 145.

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SECTION 7.0

STRÖMGREN FILTERS

The Strömgren uvby is the most widely used intermediate-band photometric system and isoften used instead of the Johnson UBV system. The letters u, v, b, y refer to the colorsultraviolet, violet, blue and yellow respectively. Because these filters have a narrow passband,the system is totally filter defined, and variations in detector spectral response, telescopetransmission, and the second order terms used for the extinction corrections and thetransformation equations can be safely ignored. In addition, the use of these filters providesmore useful astrophysical information than the Johnson UBV system.

The Strömgren filters offered by Optec are manufactured by Spectro-Film of Woburn,Massachusetts to our specifications. Spectro-Film has been making the Strömgren filters forprofessional observatories worldwide for the last 10 years and is considered a primary sourcefor these filters. When used with any CCD camera these filters will match the results frommost photometry programs throughout the world. Table 7-1 lists the optical specifications ofthe Strömgren filters. Table 7-2 lists the physical specifications of the Optec Strömgrenfilters.

OPTICAL SPECIFICATIONSCenter

Filter Wavelength Bandpass Typeu 342 nm 25 nm 6mm UG11 + 1mm WG345v 410±2 nm 16±1.6 nm interferenceb 470±2 nm 19±1.9 nm interferencey 550±2 nm 24±2.4 nm interference

Table 7-1. Optical specifications of the Strömgren filters.

The vby filters are multiple cavity interference type using dielectric quarter wave stacks withspacers of metal film. They have excellent transmission characteristic and long life whenproperly stored. However, all interference filters can be damaged when exposed to highhumidity for long periods of time. When not used, these filters should be stored in a glass jarwith a small amount of desiccant added to keep the air dry. In such an environment, thesefilters will last virtually forever.

PHYSICAL SPECIFICATIONSDiameter 12.7±0.15 mm

Thickness 7.0±0.3 mmSurface Quality 80-50

Wedge Not to exceed 5 ARC minutes

Table 7-2. Physical specifications of the Strömgren filters.

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The u filter is made from 2 pieces of Schott colored glass. The first glass of UG11 defines thered side of the pass band and the WG345 defines the blue side. The small amount of red leakof the UG11 glass beyond 700 and 750 nm should not be a source of error except for veryred stars. The surface of the UG11 glass has poor resistance to weathering (humidity) andmust be protected in a manner similar to the vby filters. Unlike the interference filters whichcannot be restored, the weathered surface of this filter can be repolished. If a small amountof weathering is observed, a white haze on the surface, a Q-tip with jewelers rouge and watercan normally repolish the surface. Use light pressure and blow dry the filter immediatelyafterwards.

A paper entitled "A Short Tutorial on Strömgren Four-Color Photometry" by Dr. DavidCrawford has been reprinted and is available free of charge. Contact Optec for details.

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SECTION 8.0

PFE-1A AUTOMATIC OPTION

8.1 PHYSICAL CHARACTERISTICS

The PFE-1A CCD photometer allows for automatic selection of filters using the 6-positionfilter sliders. A small 4-phase stepper motor is located below the flip mirror of the camerahead and provides the torque and positioning accuracy needed to exactly center the desiredfilter. A bevel gear arrangement connects the stepper to the filter slider.

The 12 VDC power requirement of the stepper motor is supplied through a 9-pin circularAmp connector, as are the four stepper control lines. The important physical and electricalspecifications for the motor used in the PFE-1A is listed in Table 8-1.

Number of Phases 4Step Angle (full step) 7.5 degreesSteps per Revolution 48

Holding Torque 2.8 oz.-in.Operating Temp. Range -15 to +50° C

DC Operating Voltage 12 voltsResistance per Winding 70W

Table 8-1. Specifications for Model PF35T-48C Stepper Motor from Nippon.

8.2 DETERMINING FILTER POSITION

Each filter position is separated by 33 full steps of the stepper motor. In order to determineposition, 165 or more full steps in either direction are delivered by the stepper motor to homethe slider against one side of its mounting. After this homing procedure, the computer orcontroller determines position by keeping track of the number of 33 step intervals from thehome position. Stalling the motor against its mounting will not harm the motor or mountingcovers in any way.

The pulse rate to the stepper can be varied under computer control and the optimum rate(fastest position change without losing steps due to slider inertia), with or withoutacceleration, must be determined experimentally. For a first approximation, try a steady pulserate of 100 steps per second and observe whether the positions are kept accurately whenchanged repeatedly.

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8.3 CONNECTING & OPERATING STEPPER MOTOR

If the SSPCARD and associated cable are purchased with the PFE-1A, this section can bedisregarded.

A 9-pin AMP connector is supplied with the PFE-1A for those wishing to design and buildtheir own stepper controller or computer interface. Table 8-2 lists the pin numbers of the 9-pin connector which are connected to the motor and the proper step sequence that theselines must follow.

FUNCTION Q3 Q1 Q4 Q2 COMMONMOTOR connectWIRE COLOR black orange brown yellow red & red

PIN NO. FORPFE-1A CONN. 7 4 3 2 1

STEP 1 On On Off OffSEQUENCE 2 Off On On OffC.W. ROT. 3 Off Off On On

4 On Off Off On1 On On Off Off

Table 8-2. Function and Color Code of Motor Wires Inside Unit.

Table 8-3 lists the pin numbers of the 9-pin AMP connector and their associated function.Either a shielded or unshielded 9-wire cable can be used. Since the amount of current usedby the stepper motor is just a few hundred milliamps, small gauge wire can be used in thecable. Cables of lengths up to 100 feet have worked successfully.

8.4 USING THE SAA1027 STEPPER DRIVER

The Signetics SAA1027 stepper motor drive IC is available from Optec for a small charge.This 16-pin IC allows easy control of the stepper motor and requires only a few externalresistors, a 12 V DC power source and a two control lines from the computer or controller.A typical circuit is shown in Figure 8-1.

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PIN NUMBER15-PINSUB-D

9-PINCIRC.

CABLECOLOR

FUNCTION

1 1 Red +12 Volts DC2 3 Orange Q4 - Pin #11 on SAA10273 7 Purple Q3 - Pin #9 on SAA10274 2 Brown Q2 - Pin #8 on SAA10275 5 N/A Not Connected6 6 White +12 Volts DC7 4 Blue Q1 - Pin #6 on SAA10278 8 Black Power Ground9 9 N/A Not Connected

Table 8-3. Pin Number and Function for the Motor Control Cable Connector.

Figure 8-1. Typical Stepper Control Circuit Using the SAA1027.

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APPENDIX A

PFE-1 MOUNTING KIT INSTRUCTIONS

MOUNTING KITS FOR THE SPECTRASOURCE INSTRUMENTS CAMERAS

The Lynxx PC, Lynxx MC, Lynxx 2, and Lynxx 2000 camera heads are shipped with acombination 1¼"/2" telescope coupler which must be removed. Loosen and remove thecoupler by removing the three socket cap screws holding the coupler to the camera face.Install the stainless steel mounting plate with the dovetail mount away from the camera faceusing the three 1/4" long flat head socket screws.

Next, attach the PFE-1 to the dovetail by tightening each of the four setscrews on the PFE-1.Roughly center the camera by looking down the 1¼" coupler. You may need to flip themirror out of the way and remove the filter slider. The CCD photometer is now ready for thereticle alignment (Section 3.3).

MOUNTING KITS FOR THE SBIG ST-4 AND ST-5 CAMERAS

To mount the PFE-1 to the ST-4, the existing 1¼" coupler with clear glass window must beremoved. Since this procedure directly exposes the CCD chip, it should only be done in adust-free environment. To reduce the moisture content inside the CCD chamber and reducethe possibility of frosting, the existing 1¼" coupler should only be removed when therelative humidity is below 50%. Carefully loosen and remove the four socket cap screws.Gently lift the telescope coupler up and away from the camera body. This will expose theCCD chip directly. Next, position the new camera mount with O-ring and clear glasswindow directly over the CCD. Line up the screw holes and install the four 5/8" long socketcap screws. Tighten snugly.

Next, install the stainless steel mounting plate with the dovetail mount away from the cameraface using the three 1/4" long flat head socket screws.

Finally, attach the PFE-1 to the dovetail by tightening each of the four setscrews on the PFE-1. Roughly center the camera by looking down the 1¼" coupler. You may need to flip themirror out of the way and remove the filter slider. The CCD photometer is now ready for thereticle alignment (Section 3.2).

Note: the eyepiece height is lower for the ST-4 than for the Lynxx cameras. This isdue to the fact that the TC-211 chip is actually mounted on the face of the camera headrather than within the camera head as with the Lynxx cameras. Thus, the chip can actually bebrought closer to the flip mirror of the PFE-1. The eyepiece height is set at Optec accordingto the mounting kit purchased. Do not attempt to adjust the eyepiece orientation or height.

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MOUNTING KIT FOR SBIG ST-5C AND CELESTRON PIXCEL 237/255 CAMERAS

The Celestron PixCel 237 and 255 cameras use a three piece mounting kit for attaching tothe PFE-1. SBIG sells the PixCel 237 camera directly as the Model ST-5C. The purpose ofthe three piece mount is to allow easy disconnect of the PFE-1 and attachment of either theMAXfield 0.33X or WideField 0.5X telecompressors to the CCD camera. Optec partnumber 3486 is required.

To install the mounting plate to the PixCel or ST-5C camera, assemble the three pieces byfirst placing the PixCel adapter into the PFE-1 and tighten the four setscrews in the PFE-1.Second, lay the PixCel T-adapter onto the piece just attached to the PFE-1 with thealignment pin engaging the hole in the T-adapter. Third, screw the PixCel retainer onto theassembly and tighten gently.

Now, screw the PixCel camera (or ST-5C) onto the T-adapter and tighten so that the camerais secure and not easy to rotate. DO NOT OVERTIGHTEN OR USE ANY LOCTITECOMPOUND. The camera can now be rotated to the proper position by loosening the foursetscrews holding the adapter and rotate the entire camera and adapter assembly. Tighten thefour setscrews again.

Refer to Section 3.3 for reticle alignment procedures.

Once the reticle is aligned and the proper rotation is obtained the CCD camera can beremoved by loosening the PixCel retainer until the CCD camera is free. Be careful not todrop it. The camera can now be removed and installed at will without losing the cameraalignment to the reticle.

Keep the retainer threads clean and lubricated with contact cleaner for best operation.

For older PixCel cameras using the SBIG color wheel a separate IR blocking filter may havebeen provided. (Current SBIG ST-5C models use RGB fitlers with IR cut coatings on eachfilter). The separate 1¼" IR blocking filter can be screwed into the T-adapter before theCCD camera is attached. To maintain parfocality with the reticle, either the IR blocking filteror the Clear 1¼" window (Optec stock no. 17619) must be used for these older cameras.

MOUNTING KITS FOR MEADE CAMERAS

The Meade Pictor 416XT and 216XT cameras are shipped from the manufacturer with a1¼" barrel (telescope coupler) with a T-thread. This piece can be removed from the cameraby simply unscrewing it. Replace it with one of the mounting kits provided by Optec. ThePictor 416XT mount is a single piece adapter (Optec stock no. 17616) while the Pictor216XT mount is a three-piece design (Optec stock no. 17617). Thread the T-thread side ofthe adapter into the camera head and tighten snugly.

3

Next, attach the PFE-1 to the dovetail by tightening each of the four setscrews on the PFE-1.Roughly center the camera by looking down the 1¼" coupler. You may need to flip themirror out of the way and remove the filter slider. You may now proceed with the reticlealignment (Section 3.3).